The aim of this project is to increase the basic understanding of how innate behavior patterns (i.e., "fixed action patterns") and recognition mechanisms (i.e., "innate releasing mechanisms") are coded in and controlled by the nervous system. For this purpose, anuran (toads and frogs) acoustic behavior, i.e., calling and responses to calls, is being studied. This behavior is especially appropriate because of its relative simplicity, the species-specificity of some calls, and the fact that some calls can be elicited in essentially normal form by brain stimulation. Anurans are especially appropriate because of their high tolerance of radical surgical procedures, accessibility and simplicity of their nervous systems, and ready availability and maintenance. The main method to be used is an isolated brainstem preparation. In this technique, the brainstem of a frog is removed and placed in a tissue bath. The calling circuits are then activated by electrical stimulation and neural correlates of calling are recorded from the brainstem and attached nerves. This method will be used with electrophysiological, lesioning, neuroanatomical, and neuroendocrinological techniques to study the calling circuits of adult frogs and to study the development of these circuits in juveniles.